Field of the Invention
The invention relates to a multi-stage horizontal centrifugal pump for conveying a fluid, as well as a method for repairing or overhauling a multi-stage horizontal centrifugal pump.
Background of the Invention
Multi-stage horizontal centrifugal pumps are used in many different technological sectors, e.g. in the oil and gas industry or in industrial energy generation. In the latter field, such multi-stage pumps are used e.g. as feed pumps or boiler feed pumps in order to feed water at the required pressure to a steam generator. In such pumps, a plurality of pump stages arranged horizontally next to each other are commonly provided, with each pump stage comprising a stage casing in each of which an impeller is provided which conveys the fluid, e.g. water, from the low-pressure inlet of this pump stage to its high-pressure outlet, which is then connected to the inlet of the next stage. All impellers are arranged in a rotatably fixed manner on a common shaft, which accordingly extends through all stage casings and is driven by a power unit, e.g. an electric motor. The individual pump stages are sealed along the common shaft typically by wear rings, which are arranged or mounted in a stationary, i.e. fixed manner with respect to the stage casings. It is a standard measure that two wear rings are provided for one pump stage, namely a first wear ring on the low-pressure side that surrounds the front cover plate of the impeller, and a second wear ring on the high-pressure side fixed in position to a partition wall which conducts the fluid from the outlet of the stage to the inlet of the next stage and typically comprises a diffuser.